Chessmaster1000: I think this is very clear. There is a rule: "A player must use both numbers of a roll if this is legally possible (or all four numbers of a double)." without any exceptions. Is there any other possibility than to use the both? Using only one is breaking the game rules. Why would the last move be an exception?

If the last move is allowed to be illegal, a player might bear all pieces out at his/her first move, as Chessmaster pointed out.